A Texas safari club auctioning a permit to hunt an endangered black rhino has contacted the FBI after receiving death threats from animal rights activists, the club said Thursday.

Ben Carter, executive director of The Dallas Safari Club, said he received at least a dozen emails threatening his family unless he called off the auction, which starts Thursday and will give one person the opportunity to hunt one of the rare beasts in Namibia.

The club plans to donate the proceeds, which it said could be as much as $1 million, to rhino conservation in the African country.

"I've had death threats against my family and to members of my staff," Carter told NBC News. "A number of the emails said, 'For every rhino you kill, we will kill a member of the club.' It is some pretty crazy stuff."

Wildlife Rangers are on the frontline of the battle to save elephants and rhinos from poaching gangs. The illegal trade in rhino horn, highlighted by Prince William earlier this year, is threatening the very existence of the creatures. NBC's Rohit Kachroo reports.

FBI spokeswoman Katherine Chaumont said the agency was aware of the threats and would take further action if necessary.

Established in 1972, The Dallas Safari Club describes itself as "a gathering point for hunters, conservationists and wildlife enthusiasts."

It said in an article promoting the auction: "What do you give the man that has everything? Well, guaranteed that man hasn't hunted black rhino in Namibia before."

The government of Namibia especially chose the club to receive one of five permits it distributes annually, Carter said.

The auction is to be held amid heightened security at the club’s four-day convention, which starts Thursday and is expected to draw 45,000 people.

Carter said the fundraiser was "the first of its kind for an endangered species."

The club said that because around 50 percent of male black rhinos die from fighting other rhinos, "selectively harvesting" the animals could lead to an increase in population.

In the 1960s there were about 70,000 black rhinos in the wild, but this figure is just down to 4,000 today. According to the club nearly of these 1,800 are in Namibia.

A new report details a massive surge in rhino poaching in South Africa, with the endangered animals now being killed for their horns at a rate of almost two a day. NBC's Rohit Kachroo reports.

Rhino horn has become more valuable per kilo than gold after a boom in Southeast Asia in its use for medicinal purposes in recent years.

Namibia’s Game Products Trust Fund will receive 100 percent of the auction money, the club said.

Wayne Pacelle, president of the Humane Society of the United States, told The Associated Press that while culling was acceptable in some instances, it was not acceptable to kill endangered species.

"We've had a standard for more than 40 years that you don't shoot an animal that's endangered," he said Wednesday.